1. Field of the Invention
This invention relates to a transducer, especially to an electro-acoustic transducer.
2. The Related Art
Referring to FIG. 1, an electro-acoustic transducer 10′ is a kind of device for converting electric energy into acoustic energy, and often known as loudspeakers. The electro-acoustic transducer 10′ includes a driving unit 20′ and a diaphragm 30′ connected with the driving unit 20′. The driving unit 20′ may come in various forms, and in this embodiment it includes a field magnet 22′ and a voice coil 24′. The field magnet 22′ is fixed inside the electro-acoustic transducer 10′ to provide a stable magnetic field, and the voice coil 24′ is movably mounted at a cylindrical gap of the magnetic field and connected with an external signal source. So when an external signal current is applied to the voice coil 24′, the voice coil 24′ will generate a magnetic force and vibrate the diaphragm 30′ back and forth axially so as to pressurize the surrounding medium (such as air) to generate a sound wave.
With the description above, it is obvious to know that the performance of the electro-acoustic transducer 10′ is determined by the ability of pressurizing the medium, and the ability of pressurizing the medium is directly proportional to the surface area and the vibration stroke of the diaphragm 30′. When the vibration stroke of the diaphragm 30′ is longer and the surface area of the diaphragm 30′ is bigger, the quantity of pressurized medium will be increased too. However, it will cause the radius and the depth of the electro-acoustic transducer 10′ to be increased. So the electro-acoustic transducer 10′ in small size can only pressurize less quantity of medium and has poor performance in general, and the electro-acoustic transducer 10′ with better performance is larger in size relatively.
Therefore, in the trend of portability and miniaturization, the electro-acoustic transducer 10′ made with conventional structure is more and more difficult to satisfy both the requirements of good performance and miniaturized size. So, an electro-acoustic transducer capable of overcoming the foregoing problems is required.